Animal health and wellness monitoring using UWB radar

ABSTRACT

A collar with an ultra-wideband radar is described. A housing contains sensor electronics and the transmit and receive antennas are located separate from the housing around the circumference of the collar. A first example of the collar includes a first transmit antenna and a first receive antenna. A second example of the collar adds a second transmit antenna and a second receive antenna.

RELATED APPLICATION INFORMATION

This application claims priority to U.S. Ser. No. 61/729,298, filed Nov.21, 2012, whose contents are expressly incorporated herein by reference.

BACKGROUND

1. Technical Field

Aspects of this disclosure relate to the use of radar in monitoringphysiological conditions of mammals.

2. Related Art

Animals, like humans, can suffer from injury or illness, negativelyimpacting their health. Timely detection of changes in health througheither regular or event driven episodic monitoring of physiologicalprocesses can enable veterinary intervention, potentially reducing theeffects of an adverse condition, improving the quality of life, andprolonging life. In particular, cardiac and respiratory monitoringprovides useful information on the health of an animal and these typesof information are commonly used to diagnose, treat, and manage theanimal.

Animals can represent a large financial and often, emotional investment.Health monitoring can help optimize veterinary care to protect thatinvestment and provide peace of mind to the owner. Monitoring isapplicable to a wide range of animals, including feed stock, breedingstock, exotic/endangered species, animal athletes, performing animals,and domestic pets. Monitoring can be accomplished whether the animal isin the wild, in captivity (e.g. a zoo or animal park), in a pasture orfree-range, in a barn or stable, at home or in the yard, in a pen or acrate.

Animal health monitoring is challenging. Many familiar sensortechnologies—e.g. ECG, pulse oxygen, ultrasound, and temperature,require direct skin contact, making them impractical for use withanimals having fur or feathers. They may also require that the sensor bepositioned on a specific location on the body which again may beimpractical. For example, assuming prior removal of the fur, pulse oxsensors typically need to be placed on thin anatomical structures suchas ears, making them prone to loss through scratching, rubbing, orshaking Similarly, ECG sensors are usually placed on the torso, inproximity to the heart and the Einthoven triangle, making them prone toloss through scratching, rubbing, or shaking Finally, there is no sensorcurrently available that is capable of providing a direct, unobtrusivemeasurement of respiration—a needed metric in understanding and managinganimal health.

The monitoring of respiration is currently under-appreciated inveterinary care and there are only a handful of researchers in thecountry studying/teaching animal pulmonology. This lack of integrationinto veterinary medicine is in contrast to the body of publishedinformation dating back several decades concerning the role ofrespiratory symptoms in the diagnosis and treatment of animal cardiacand respiratory disease. One of the obstacles in integrating respiratorymonitoring into veterinary practice is the lack of appropriatenon-invasive sensors. Most veterinarians are forced to rely on manualobservations—watching the animal, to obtain respiratory data. Theseobservations are of limited use and complicated by the visit to the vetas this usually leads to animal anxiety and elevated cardiopulmonaryfunctions that are not representative of the animal's true underlyinghealth. Respiratory monitoring is not viewed as an important parameterbecause of the difficulty in obtaining accurate data.

Respiratory monitoring in the animal's nature environment—e.g. at homefor a pet or in a pasture for a horse or cow, would be a benefit toveterinary medicine as the data would be more representative of theanimal's actual state of health. This data could be used to help treatanimals with known medical problems as well as identify animals that maybe developing medical problems. There are a number of medical problemsthat exhibit respiratory symptoms, including heart disease, heartmurmur, pulmonary edema, pulmonary fibrosis, sleep apnea, COPD, asthma,larynx paralysis, kennel cough (bordetella), and others. Specific todomestic pets, respiratory monitoring would be important withbrachycephalic dogs—breeds with short muzzles such as bulldogs,cavaliers, pugs, Boston terriers, Boxers, Pekingese, shih tzu, etc.These breeds have a high incidence of respiratory problems and areinefficient “panters”, leading to inflamed respiratory tracts andlaryngeal problems as well as making them much more susceptible to heatstroke. Timely identification of respiratory distress would enableearlier and less complicated/expensive intervention and reduce the riskto the animal.

As discussed above, many medical monitoring technologies are impracticalor unusable with animals. Doppler radar approaches, whether CW orpulsed, have been investigated as a technique for collectingcardiopulmonary data. They have generally relied on off-body ornon-contact monitoring where the Doppler radar sensor is separated fromthe subject by an air gap and thus, does not make direct contact withthe patient. Due to the large difference between the relative dielectricproperties of the primary propagation medium (air, where ∈_(r)=1) andliving tissue (∈_(r)≈50), most of the RF energy is reflected at the skinsurface with little energy propagating into the interior of the body tointerrogate the internal organs. Any energy that does propagate into thetorso and is subsequently reflected by the internal organs is greatlyreduced by internal tissue absorption as well as a second transitionacross the skin-air boundary, resulting in little energy from theanatomical target making it back to the receiver. Low returns equate tomarginal data.

A common technique for isolating a specific physiological processinvolves combining Doppler with auto-correlation. Auto-correlationsamples the time-domain waveform and correlates the Nth pulse with aperiod of time after the Nth pulse where the period is centered on theanticipated rate of the specific physiological process under reviewbased on the Doppler results. High correlation coefficients equate togreater confidence that the system has locked onto the specificphysiological process. An externally defined threshold is often used todetermine adequate correlations and thus, sufficient target acquisition.

Because of the strong surface component associated with respiration(typically 1 cm chest wall displacement in an average adult male),off-body techniques can collect reasonable pulmonary data but thosephysiological processes that do not have strong surface components, suchas cardiac activity, are difficult to detect and measure with Doppler.Another limitation of Doppler is its general inability to distinguishmotion associated with more than one physiological process when thoseprocesses operate at similar rates. For example, in subjectsexperiencing bradycardia, the cardiac rate will approach and sometimedrop below the respiratory rate, making it difficult for Doppler todistinguish the two processes from each other.

SUMMARY

Once or more aspects relate to a collar with an ultra-wideband radar. Ahousing contains sensor electronics and the transmit and receiveantennas are located separate from the housing around the circumferenceof the collar. A first example of the collar includes a first transmitantenna and a first receive antenna. A second example of the collar addsa second transmit antenna and a second receive antenna. The antennas maybe positioned to obtain position and movement information from variousinternal structures including a carotid artery, a jugular vein, andmuscles surrounding an esophagus and trachea.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an illustrative example of a monostatic radar on the neck ofan animal in accordance with one or more embodiments.

FIG. 2 is an illustrative example of a bistatic radar on the neck of ananimal in accordance with one or more embodiments.

FIG. 3A is a first illustrative example of a multistatic radar on theneck of an animal in accordance with one or more embodiments. FIG. 3Bshows signal paths for the multistatic radar of FIG. 3A.

FIG. 4A is a second illustrative example of a multistatic radar on theneck of an animal in accordance with one or more embodiments. FIG. 4Bshows signal paths for the multistatic radar of FIG. 4A.

FIG. 5A shows an illustrative example of a multistatic radar on a narrowneck of an animal in accordance with one or more embodiments. FIG. 5Bshows signal paths for the multistatic radar of FIG. 5A.

FIGS. 6A and 6B are charts showing cardiac and respiratory rates from asternal position of a UWB sensor on an animal in accordance with one ormore embodiments.

FIGS. 7A and 7B are charts showing cardiac and respiratory rates from aright carotid position of the UWB sensor

FIGS. 8A and 8B are charts showing cardiac and respiratory rates fromright larynx position of the UWB sensor

FIGS. 9A and 9B are charts showing cardiac and respiratory rates fromposterior neck position of the UWB sensor

FIGS. 10A and 10B are charts showing cardiac and respiratory rates fromright femoral position of the UWB sensor

FIGS. 11A and 11B are charts showing cardiac and respiratory rates fromright shoulder position of the UWB sensor

FIG. 12 shows an illustrative example of a UWB sensor.

DETAILED DESCRIPTION

The following description relates to configurations of ultra-wideband(UWB) sensors for obtaining physiological information from mammals.Specifically, aspects of the disclosure pertain to the use of UWBsensors as medical radar to the extent they use very low power UltraWide Band (UWB) radio frequency (RF) energy. In practice, the UWBmedical radar emits a narrow pulse of electromagnetic energy, whichpropagates into a body. As the energy enters the body, small amounts ofthe incident energy are reflected back to the device. The reflectionsare due to the differences in dielectric properties of the illuminatedtissues and organs. The reflected energy is then received and processedusing application-specific signal processing algorithms to extractinformation on the type, location, size, and motion of the illuminatedtissues and organs. It is appreciated that the greater the dielectricconstant between illuminated tissues and organs increases the reflection(or backscatter) of the electromagnetic pulse.

Examples of UWB medical radar systems are found, for instance, in U.S.Pat. No. 7,725,150 to Tupin, Jr. et al. and U.S. Pat. No. 8,463,361 toTupin, Jr., both assigned to LifeWave, Inc. of Los Altos, Calif., whosecontents are expressly incorporated by reference to their entirety.

Ultra-wideband radar overcomes one of the limitations found with Dopplerradar because of the extremely fine radial resolution (<5 mm) inherentwith UWB radar, allowing the UWB sensor to more easily isolate differentphysiological processes based on their unique locations within thepatient. The sensor can focus on one or more depths using traditionalrange sweep techniques and, if the sensor is configured as an array,further focal processing techniques based on beam-steering andbeam-forming can be applied.

A contact-based UWB medical sensor for monitoring the health of animalshas several distinct advantages over Doppler and off-body monitoring.The UWB radar does not need direct skin contact or coupling gels,allowing it to collect useful physiological data through fur or feathersyet by maintaining contact with fur or feathers. As such, the largereflective losses associated with the skin-air interface aresignificantly reduced. Second, assuming the electronics are sufficientlyprotected from the environment (e.g., sealed against rain and moistureor otherwise moisture resistant), the radar may operate when wet ordirty.

For instance, a UWB radar system may be placed on an animal's collar asshown in FIG. 1. FIG. 1 shows a cross-sectional view of an animal's neckand the collar being worn by the animal. The UWB radar system of FIG. 1includes sensor electronics 101 in a housing and antennas 103 includinga transmit antenna 104 and a receive antenna 105. The antennas 104 and105 may be placed together in a singular housing 103 a or may be housedseparately. One advantage of housing the antennas 104 and 105 togetheris that the direction each antenna faces may be fixed with respect tothe other antenna.

These components of the UWB radar system may be co-located at a singlelocation or may be placed around the collar 102 as shown in FIG. 1 andconnected by wires, cables, traces on a circuit board (rigid orflexible), or other known electrical connecting techniques. Ifco-located, an example of a size of the combination of the antennas 104and 105 and the sensor electronics 101 may be 7.4 cm×2.3 cm×1.8 cm andweigh 29 g.

The UWB radar system monitors movement of different structures based ontheir different dielectric constants relative to surrounding structuresor tissues. The change in location of the interfaces between thesestructures is monitored by the UWB radar system and is subsequentlyanalyzed through known analysis techniques of UWB radar signals.

Aspects of this disclosure relate to configurations of the UWB radarsystem to provide improved signals for analysis. For reference, FIG. 1shows the animal's neck 108 with skin 109, trachea 110 with surroundingmuscles 111, 112, esophagus 113 with surrounding muscles 114, 115,carotid arteries 116, 117, jugular veins 118, 119, spinal column 122,and various other muscles (including lower muscle groups 120, 121, andupper muscle groups 123 and 124).

In one example, the UWB radar system with sensor electronics 101 andantennas 103 may be co-located (namely, the sensor electronics 101module being positioned radially outward from antennas 103 relative toneck 109) as a monostatic radar structure and hang off collar at abottom-most position 107 relative to the animal's neck 108, closest tothe trachea 110.

In another example, as shown in the configuration of FIG. 1, sensorelectronics 101 are positioned at the top of the neck 108 with theantennas 103 located on the side of neck 108, also as a monostatic radarstructure. Here, by placing transmit antenna 104 and receive antenna 105closer to carotid artery 116 and jugular vein 118, the beam from thetransmit antenna 104 and returning to receive antenna 105 may encounterfewer dialectically different structures when located at the positionshown in FIG. 1 then when located at position 107. This reduction in thenumber of dialectically different structures reduces backscatter signalsfrom those different structures.

As depicted, collar 102 may include a counterweight 106 that may beapproximately the weight of antennas 103 balance the UWB radar systemand attempt to maintain antennas 103 at their side placement around theneck 108.

Alternatively or in addition to counterweight 106, a tensioner may beused to maintain a relatively constant tension on collar 102 to helpposition antennas 103 on the side of the neck 108.

Further, as larger animals have stronger neck muscles (for instancemuscles 123, 124), these muscles in some instances may form a recess 125upward of spinal column 122. The inside shape of sensor electronics 101may be convex to allow at least some nestling in the concave recessformed by muscle groups 123 and 124.

By placing antennas 103 and aside position as shown in FIG. 1, accuratereadings from the animal's carotid artery 116 and/or jugular vein 118may be obtained. Depending on the type of animal, the antennas 103 maybe angled relative to neck 108 and/or to each other to allow forillumination of relevant structures and collection of backscatteredsignals from those structures. For instance, to concentrate solely oncarotid artery 116, the receive antenna 105 may be moved closer totransmit antenna 104 to receive the stronger backscatter signals roughlyin line with the radiated beam from transmit antenna 104 plan.Alternatively, to concentrate on carotid artery 116 and the movement ofmuscles 114 and 115 surrounding esophagus 113, receive antenna 105 maybe moved farther away from transmit antenna 104. Further, to alsoinclude signals from the movement of muscles 111 and 112 surroundingtrachea 110, the receive antenna 105 may be moved further from transmitantenna 104. In these examples, the various muscle groups may bemonitored surrounding the trachea 110 as the trachea's cartilage may notreflect the UWB pulses and the movement of the cartilage is notdetectable directly.

In many applications across a range of species, the UWB radar sensor canbe placed within or on a collar or harness where the choice of thegarment and specific sensor placement upon or within the garment isdriven by the desired medical data, the need to locate the sensor in theproximity of the key primary and alternative secondary anatomicalstructures required to obtain the desired data, and the need to securethe sensor to the animal such that it is unlikely to be dislodged orremoved during normal activity. In addition, the shape of the sensor andits antennas can be modified to take advantage of the anatomy to assistwith placement and maintain position.

Actual signal processing and display of results does not have to beco-located with the sensor and in fact, remote processing and displaymight be highly desirable. The data can be processed (partially orcompletely) locally using an embedded processor (for instance,microcontroller or discrete signal processor) or wirelessly transferredto another processing platform—dedicated base station, smart phone,tablet, PC, or the cloud using a conventional wireless transfer system(transmitter in the sensor electronics 101 to transmit a signal to ofreceiver over, for instance a Wi-Fi connection). The display can be adigital readout on a panel built into the base station or take advantageof the GUI capabilities of any number of consumer electronics.

Of the various limitations described herein, a collar 102 allowscollection of basic cardiopulmonary data without the need to be directlyover the heart and lungs. The collar with its UWB radar system collectsdata primarily from the carotid arteries in the neck, as well asphysiological data associated with motion of the larynx, trachea, andesophagus. Data from these structures enables monitoring ofconsumption—i.e. food and water, vomiting and regurgitation, as well asenabling the detection of choking and vocalization—e.g. barking, orother processes involving the larynx and trachea based on analyses ofreceived signals including identification of the frequency components ofthe signals, the magnitude of those frequency components, and how thosesignals change over time. Other sensor technologies may be added to theassembly to support data fusion for improved accuracy, reliability, andnoise reduction.

Further, an additional counterweight (e.g., the animal's tag or othercollar attachment) may be provided at location 107 to provide a weightthat may further aid in aligning the sensor electronics 101 and antennas103.

FIG. 2 shows another configuration of sensor electronics 201 and theantennas. In FIG. 2, transmit antenna 204 is located on a first side ofneck 108 and receive antenna 205 is located on a symmetrically oppositeside of neck 108. Here, the antennas 204 and 205 may be symmetricallydistributed around the circumference of the neck 108 to maintain an evenweight distribution on collar 202. One example of this configurationwould have the sensor electronics 101 in the depression over the spinousprocess 125—see FIGS. 1 and 2, enabling easy and consistent placement ofthe sensor electronics 201. Unlike the anterior of the neck where manyanimals have a wattle and are sensitive to any object, this locationtypically has less fat tissue, less loose skin, and has less anatomicalvariation within a specific species or breed.

The configuration of transmit antenna 204 being separate from receiveantenna 205 FIG. 2 is commonly referred to as a bistatic radararchitecture. In the minimal separation case, both the TX and RXantennas may be located along the spine while in the limit, they couldbe located on either side of the larynx.

In FIG. 2, the receive antenna 205 may receive backscatter from somestructures inside neck 108. For structures that have a strong dielectricdifference from surrounding structures, the amplitude of the backscattersignals may predominate the received collection of signals. However forstructures that have a less significant dielectric difference fromsurrounding structures, the resultant backscatter from these lesssignificant dielectric differences is weaker. Thus, when attempting tomonitor movement of different structures relative to each other wherethe dielectric constants of these structures are relatively close to oneanother, monitoring backscatter signals is more difficult. In thissituation, monitoring signal modification (signal amplification,attenuation, polarization, retardation or advancement, and the like)with a receive antenna 205 generally facing transmit antenna 204 ispreferable.

The above bistatic of FIG. 2, configuration could be expanded to amultistatic configuration with a corresponding increase in weight, costof goods, and power consumption. As shown in FIG. 3A, the sensor mayinclude two radar channels 303 and 306, each consisting of a TX and RXpair (304/305 and 307/308, respectively), where one radar channelinterrogates the right side of the neck and one radar channelinterrogates the left side.

This configuration takes advantage of the symmetry in the neck toimprove signal reception while reducing common noise. More radarchannels may be added for additional performance improvements.

As shown in FIG. 3B, radar channel 1 303 is shown on the left side ofFIG. 3A and radar channel 2 306 is shown on the right side of FIG. 3A.The backscatter signal 309 of radar channel 1 303 from transmit antenna304 enters and then returns back through the side of neck 108 to receiveantenna 305. Similarly, the backscatter signal 310 of radar channel 2306 from transmit antenna 307 enters and then returns back through side306 of neck 108 to receive antenna 308. Also, receive antenna 308receives attenuation signal 311 (from radar channel 1 to radar channel2) as originally transmitted from transmit antenna 304. Likewise,receive antenna 305 receives attenuation signal 312 (from radar channel2 to radar channel 1) as originally transmitted from transmit antenna307.

To permit attenuation signals 311 and 312 to be received and used bysensor electronics 301, common timing signals used to control thetransmission of the UWB pulses in the multistatic UWB radar system areused in radar channel 1 and radar channel 2. For instance, when transmitantenna 304 has finished transmitting, both receive antenna 305 andreceive antenna 308 may both be active (in accordance with the same or atemporally adjusted timing signal) in receiving signals scattered and/ormodified by the combination of various structures in neck 108.Alternatively, transmit antenna 304 and transmit antenna 307 maytransmit simultaneously in accordance with the same or temporallyadjusted timing signal with one of receive antenna 305 or receiveantenna 308 also being active (and likewise being responsive to the sameor temporally adjusted timing signal). Finally, transmit antenna 304 andtransmit antenna 307 may both transmit simultaneously and receiveantenna 305 and receive antenna 308 may both receive signalssimultaneously with all operations coordinated through the same ortemporally adjusted timing signal. The purpose using the same ortemporally adjusted timing signal in sensor electronics 301 is toprovide temporal coherence for the operations of radar channel 1 303 andradar channel 2 306.

FIG. 4A shows a similar structure to that of FIG. 3A in which sensorelectronics 401 controls radar channel 1 403 (with transmit antenna 404and receive antenna 405) and greater channel 2 406 (with transmitantenna 407 and receive antenna 408). Here, the locations of thetransmit antenna and receive antenna of radar channel 2 406 are flippedrelative to the locations of transmit antenna 404 and receive antenna405. While backscatter signal 409 of radar channel 1 is similar to thatshown in FIG. 3B, backscatter signal 410 is reflected more upwards thenbackscatter signal 310 of FIG. 3B (which is reflected more downwards).Also, attenuation signal 411 from transmit antenna 404 to receiveantenna 408 is generally more horizontal than attenuation signal 311.Similarly, attenuation signal 412 from transmit antenna 4072 receiveantenna 405 is also generally more horizontal than attenuation signal412.

As with the sensor electronics 301 of FIG. 3A, sensor electronics 401 ofFIG. 4A may also use temporally coherent timing signals to allow themultistatic operation of the transmit and receive antenna components ofFIG. 4A.

FIG. 5A shows a configuration similar to that of FIG. 4A but with ananimal having a narrower neck 108. FIG. 5A shows collar 502, sensorelectronics 501 (with the common timing reference providing temporalcoherence among radar channel 1 503 and radar channel 2 506), transmitantennas 504 and 507, receive antennas 505 and 508. FIG. 5B showsbackscatter signals 509 and 510 and attenuation signals 511 and 512.

In all cases (including monstatic, bistatic, and multistatic), thelocation, orientation, and antenna characteristics of the paired TX andRX antennas for each radar channel may be designed to allow convergenceof the TX and RX antenna bore sights onto the anatomical structure ofinterest while maintaining sufficient beamwidth at the structure ofinterest.

As described above, a counterweight may be integrated to minimize thepotential for collar rotation while a tensioning device (springs orclips or elastically deformable materials) may be added to maintainconstant pressure against the animal's neck 108, minimizing the noisecaused by motion at the sensor/skin interface. Also, it is important tonote that the sensor electronics and antennas do not need to beco-located as the electronics can connect to the antennas via cables orflexible circuit boards. Either of these connection techniques can beembedded into the collar itself as long as the connecting media isrelatively homogeneous to minimize RF reflections.

A harness—e.g. a modified walking harness, has the advantage of allowingone or more radars to interrogate various anatomical regions of interestor to enable more sophisticated signal processing by isolating on aparticular organ. For example, if the UWB radar sensor has at least onechannel proximal to the heart, advanced cardiac biometrics can beobtained, including stroke volume, cardiac output, and changes in bloodpressure. Similarly, if the UWB radar sensor has one channel proximal tomain right and left nodes of the lungs, the system can check forasymmetrical breathing patterns.

The UWB radar is not limited to the torso for collecting cardiopulmonarydata as there are many alternative locations on the animal that can beexploited, particularly for obtaining cardiac data. For example, goodquality cardiac data can be collected by positioning the UWB sensor inproximity of the carotid arteries to take advantage of the expansion andcontraction in the radius of the arteries throughout the cardiac cycle.In addition, positioning the sensor on the neck has been shown toprovide reasonable and quantifiable respiratory information.

Various porcine animal models (weights between 30-50 kg) have beenstudied thank you to develop new human cardiopulmonary monitoringsystems. In these studies, a UWB radar sensor was placed to the left ofthe animal's sternum, proximal to the heart and collectedcardiopulmonary data in parallel with other reference monitors. Datafrom the UWB radar sensor was processed with proprietary signalprocessing algorithms and the results correlated against the data fromthe reference monitors to determine the efficacy of the radar sensor.The UWB sensor demonstrated the ability to measure cardiac and pulmonaryrate, detect changes in cardiac stroke volume, measure CPR compressions,and determine the status of the circulatory system across a variety ofcardiac conditions.

Most recently, the ability of the sensor to measure cardiopulmonaryrates in small animals using dogs weighing less than 10 kg as the testsubjects has been studied. This ability along with the capabilitiespreviously demonstrated and described above, enables a variety of animalmonitoring applications. During the tests, the cardiac rate was manuallyobserved to be approximately 65 BPM, while the respiration rate wasmanually observed to be approximately 20 BPM.

In the first test, the UWB radar sensor was placed on the left side ofthe animal's rib cage, approximately level with the heart while theanimal was prone. As can be seen in FIGS. 6A and 6B, the cardiac rateand pulmonary rate as calculated with an FFT were readily discernibleand matched manual measurements.

In the second test, the UWB radar sensor was placed on the right side ofthe animal's neck, over the carotid artery with the axis of the sensorparallel to the longitudinal axis of the artery. As can be seen in FIGS.7A and 7B, the cardiac rate and pulmonary rate as calculated with an FFTwere readily discernible and matched manual measurements.

In the third test, the UWB radar sensor was placed on the right side ofthe animal's neck, immediately adjacent to the larynx with the axis ofthe sensor parallel to the longitudinal axis of the trachea. As can beseen in FIGS. 8A and 8B, the cardiac rate and pulmonary rate ascalculated with an FFT were readily discernible and matched manualmeasurements. This position is particularly interesting because it alsoprovides a view of the larynx, trachea, and esophagus.

In the fourth test, the UWB radar sensor was placed on the posterior ofthe animal's neck, immediately over the spinous process with the axis ofthe sensor parallel to the longitudinal axis of the spine. As can beseen in FIGS. 9A and 9B, the cardiac rate and pulmonary rate ascalculated with an FFT were readily discernible and matched manualmeasurements.

In the fifth test, the UWB radar sensor was placed on the right hindleg, immediately over the right femoral artery and below the pelvicjoint, with the axis of the sensor parallel to the longitudinal axis ofthe artery. As can be seen in FIGS. 10A and 10B, the pulmonary rate ascalculated with an FFT was readily discernible and matched manualmeasurements. The cardiac rate was less discernible and somewhatobscured by other noise sources.

In the sixth test, the UWB radar sensor was placed on the right foreleg, immediately over the right auxiliary artery and below the shoulderjoint, with the axis of the sensor parallel to the longitudinal axis ofthe artery. As can be seen in FIGS. 11A and 11B, the pulmonary rate ascalculated with an FFT was readily discernible and matched manualmeasurements. The cardiac rate was less discernible and somewhatobscured by other noise sources.

To summarize these basic cardiopulmonary tests with the UWB medicalradar on a canine model, the cardiac and pulmonary rates as calculatedfrom the UWB radar data were generally discernible and matched manualmeasurements. In several instances, the cardiac rate was lessdiscernible than pulmonary and somewhat obscured by other noise sources,potentially including muscle twitch from the animal and the researcherholding the sensor in position. Similarly, in several instances, thepulmonary rate varied slightly over 2-3 BPM, most likely due to theresolution of the FFT (˜0.732 BPM) and the expected variability inrespiration from its voluntary component (observed as minorbreath-holding). It is interesting to note that the strength of thecardiac signal was typically 10-13 dB below that of the pulmonary signalwhile neck and torso positions produced more discernible cardiopulmonarydata with minimal noise.

FIG. 12 shows a conventional configuration for a UWB radar system asknown in the art. The UWB radar system of U.S. Pat. No. 7,725,150 isincorporated herein by reference. The controller 1201 generates thetiming and control signals 1201 a, 1201 b, 1201 e, 1201 d, and 1201 e tosynchronize and manage the rest of the system. It also accepts internalfeedback signals from the other subsystems, accepts external controlinputs from an operator, and has the capability of providing dataoutputs to the operator or medical record system. The controller can berealized using an integrated processor and associated circuitry.

Based on timing and control signals 1201 a from the controller 1201, thepulse repetition frequency (PRF) generator 1202 creates the basebandpulse train used by the transmitter 1203 and, after range delay Δt 1205,by the receiver 1206. Alternately, both the transmitter 1203 and thereceiver 1206 may receive a delayed signal from the pulse repetitionfrequency generator 1202. Further, the delay applied to either or bothof the transmitter 1203 and the receiver 1206 may be fixed or variable.

Since the pulse train is common to both the transmitter and receiversubsystems and allows them to operate synchronously, the system is atime-coherent radar system. In practice, a voltage-controlled oscillator(VCO) operating at a nominal but only exemplary output frequency of 2MHz in or associated with the PRF generator supplies the pulse train.Randomized pulse-to-pulse dither can be added to the output of generator2 by injecting a noise signal from a noise signal source (not shown)into the VCO control port. The random dither causes spectral spreadingto reduce the probability of interfering with other electronic devicesas well as provide a unique transmit coding pattern per unit, allowingmultiple units to operate in close proximity without substantial concernfor mutual interference.

Transmitter 1203 generates a series of low-voltage, short-durationpulses 1203 a (in one embodiment, less than 200 ps) based on the pulsetrain from the PRF generator 1202. In practice, differentiating theedges of a pulse train having extremely fast rising and falling edgescreates the sub-nanosecond pulses. Through the combination of thetransmitter and the antenna, the short duration pulses are convertedinto an ultra-wide band spectrum signal centered in the RF/microwavefrequency bands in accordance with FCC R&O 02-48.

In one embodiment, the transmitter 1203 and receiver 1206 share a commonantenna 1204. In another embodiment, the antennas are separated intotransmit antenna 1204 a and receive antenna 1204 b. For the transmitter,the antenna 1204 a couples the short pulses from the transmitter 1203 tothe environment, as illustrated at A, to a patient. Subsequently,reflections B are received from the environment and fed to the receiver1206. Various antenna configurations may be used including: commerciallyavailable horns and flat resonators, simple magnetic dipoles, and amagnetic dipole or “loop” antenna(s) with a diameter selected tooptimize the transmission and reception of UWB signals. For example, aloop antenna with a diameter of 4 cm fabricated from 24-gauge solidcopper wire was used in conjunction with a UWB system operating with a10 dB bandwidth of 1.5 Ghz to 3.4 Ghz.

Based on timing and control signals 1201 b from the controller 1201 andthe pulses originating from the PRF generator 1202, the range delay Δt1205 generates a delayed version of the PRF timing signal. The output ofthe range delay triggers a sample-and-hold circuit, describedsubsequently, in the receiver 1206 where the delay value is chosen tocompensate for fixed electrical delays within the system and focus datacollection to those reflections originating from a specific depth withinthe body. The range delay is extremely flexible and, in conjunction withthe controller, can generate a large range of delay profiles toaccommodate a variety of signal processing requirements.

There are two delay modes used to collect medical data—range gate modeand range finder mode. In range gate mode, the depth within the bodythat corresponds to the area for which physiological data is to beextracted is fixed and a large number of samples are collected at thatdepth over a period of multiple seconds in one example, providinginformation on relative changes within the body. The depth can then bechanged and the process repeated. In contrast, when operating in rangefinder mode, the depth is swept repeatedly over a finite range ofinterest, with samples collected at each depth. Range gate mode providesdetailed information at the depth of interest while range finder mode isused to quickly collect data over a range of depths. A range delaycircuit supports both range gate and range finder modes. In practice,the range delay circuit can be realized using a 12-bit digital-to-analogconverter (DAC), an operational amplifier, used to realize functions,and a one-shot multivibrator. The one-shot multivibrator (an LMC555 canbe used, as one example) generates a delayed version of the transmittedpulse train in response to signals received on its two controlinputs—trigger and hold-off. The pulse train from the PRF generator 1202is the trigger signal and causes the one-shot multivibrator to initiatea single pulse cycle for each pulse in the pulse train. The hold-offvoltage determines the period of the pulse. By varying the hold-offvoltage, different pulse periods, and thus different delay values, canbe generated. The amount of delay is set by both analog and digitalcontrols. The analog controls set the minimum delay value and theallowable range of control while the digital controls are used todynamically adjust the actual delay value, delay sweep rate, andresolution of delay control.

In practice, a 12-bit data value—Data_(x), corresponding to the desireddelay is sent from the controller 1201 to the DAC. The DAC produces avoltage V_(x) where: V_(x)=4.096 Volts×(Data_(x)/4096).

The DAC output voltage and a DC voltage are added together in a summingjunction and the sum is amplified and fed to the hold-off control inputof the one shot. The DC voltage level, in conjunction with the amplifiergain, set the minimum delay value and the allowable range of control.Both the DC voltage level and gain settings are controlled by manualadjustment of potentiometers. A delay range of 5 ns has been proven toyield good quantitative data in cardiopulmonary applications andcorresponds to a depth range of approximately 12 cm into the body. Otherdelay range values of up to 10 ns have also shown to produce usable datasets.

The receiver 1206 processes the raw reflections received from theantennas 1204 b over line 1204 b 1 in the analog domain to optimize thesignals of interest. For cardiopulmonary data, this includes suppressingthe high-strength static return signals and amplifying the motionartifacts. Receiver 1206 may be based on a dual-channel balancedreceiver architecture where the transmitter pulses are capacitivelycoupled from the output of the transmitter 1203 into both receivechannels via RF. Splitter and the antenna 1204 is connected or otherwisecoupled to one channel. The balanced receiver architecture provides ahigh degree of common mode rejection as well as differential gain. Thecommon mode rejection provides a significant amount of attenuation tosignals common to both channels thus minimizing interference from thetransmit signal with the desired receive signal. The differential gaininherent in this architecture amplifies signals unique to either channelthus the received signal, being unique to the channel, is amplified.

Both channels can use an ultra-fast sample-and-hold (S/H) circuit, eachtriggered by the delayed impulse train created by the pulse generatorusing the delayed pulse train over the line from the range delay circuitΔt 5 of FIG. 12. The active sampling window is set at approximately 320ps in one example and can be easily modified by selectively changing thevalue of a single passive component. The outputs of the two S/H circuitsare integrated over multiple samples in integrator elements to improvethe signal-to-noise ratio. The integrated samples feed the inverting andnon-inverting inputs of an instrumentation amplifier, attenuating thetransmitted signal and amplifying the received signal.

As illustrated in FIG. 12, A/D converter 1207 (ADC) is controlled bycontroller 1201 through control lines 1201 e. The controller sets thesample rate, sample resolution, and start/stop timing for the samplingprocess based on the mode of operation. The ADC digitizes the enhancedanalog motion reflections from the receiver 1206, translating theenhanced reflected energy into a series of discrete digital values. Asone example in range gate mode, 16,000 samples per second at 16-bit persample may be used.

The digitized signal from the A/D converter 1207 is then processed toextract pertinent physiological information in signal processor 1208 perFIG. 12. The signal processing block is extremely flexible and, asmentioned previously, can accommodate a wide variety of algorithms insupport of different medical applications. In addition the algorithm canbe implemented using parallel, serial, or hybrid parallel/serialarchitecture. The choice of a specific architecture is left to thoseskilled in the art and will depend on the application and other systemconstraints. The controller manages the signal processing operationsthrough control path 1201 d.

The resultant physiological data is displayed on a user interface (notshown). This can include tracings of amplitude versus time for one ormore depths of interest, power spectral density for one or more depthsof interest, time domain and frequency domain histograms for a range ofdepths, numerical values for heart and/or lung rates, as well as theassociated confidence factors for the displayed data, as describedsubsequently. The controller 1201 of FIG. 12 converts the data from thesignal processor to an operator-friendly format through control path1201 e for display on the user interface.

What is claimed is:
 1. A collar comprising: a housing containing aprocessor configured to control generation of an ultra-wideband radarsignal and reception of one or more resultant signals, said housinglocated at a first circumferential position on said collar; a transmitantenna separate from the housing, the transmit antenna configured tooutput the ultra-wideband radar signal directed at biological tissue,the transmit antenna having a beam width; and a receive antenna separatefrom the housing, the receive antenna configured to receive the one ormore resultant signals based on a reflection of the ultra-wideband radarsignal from the biological tissue, the receive antenna having a beamwidth, wherein the transmit antenna is located at a secondcircumferential position on said collar that is different from saidfirst circumferential position, and wherein the transmit antenna islocated at a fixed angle relative to the receive antenna to maximize amagnitude associated with the one or more resultant signals such thatthe beam width of the transmit antenna is configured to overlap with thebeam width of the receive antenna at the biological tissue.
 2. Thecollar according to claim 1, further comprising a second housing,wherein the housing containing the processor is a first housing, andwherein both the transmit antenna and the receive antenna are located insaid second housing.
 3. The collar according to claim 1, wherein thereceive antenna is located at a third circumferential position on saidcollar that is different from each of said first circumferentialposition and said second circumferential position.
 4. The collaraccording to claim 1, further comprising a counterweight located at athird circumferential position on said collar, said thirdcircumferential position being different from said first circumferentialposition and said second circumferential position.
 5. The collaraccording to claim 1, further comprising a tensioner located at a thirdcircumferential position on said collar, said third circumferentialposition being different from said first circumferential position andsaid second circumferential position.
 6. The collar according to claim1, wherein the transmit antenna is a first transmit antenna, wherein thereceive antenna is a first receive antenna, and wherein the collarfurther comprises: a second transmit antenna; and a second receiveantenna.
 7. The collar according to claim 6, wherein the first transmitantenna is circumferentially closer to said housing than said firstreceive antenna, and wherein the second transmit antenna iscircumferentially closer to said housing than said second receiveantenna.
 8. The collar according to claim 6, wherein the first transmitantenna is circumferentially closer to said housing than said firstreceive antenna, and wherein the second receive antenna iscircumferentially closer to said housing than said second transmitantenna.
 9. The collar according to claim 6, wherein, when the firsttransmit antenna outputs said ultra-wideband signal, said first receiveantenna receives said one or more resultant signals.
 10. The collaraccording to claim 6, wherein, when the first transmit antenna outputssaid ultra-wideband signal, said second receive antenna receives saidone or more resultant signals.
 11. The collar according to claim 6,wherein, when the first transmit antenna outputs said ultra-widebandsignal, said first receive antenna and said second receive antennareceive one or more resultant signals.
 12. The collar according to claim6, wherein, when the first transmit antenna and the second transmitantenna output said ultra-wideband signal, said first receive antennareceives one or more resultant signals.
 13. The collar according toclaim 1, wherein the transmit antenna is configured to output theultra-wideband signal to illuminate at least one of a carotid artery anda jugular vein, and wherein the receive antenna is configured to receivethe one or more resultant signals containing information relating to theposition and motion of said at least one of the carotid artery and thejugular vein.
 14. The collar according to claim 1, wherein the transmitantenna is configured to output the ultra-wideband signal to illuminatemuscles proximate to at least one of a trachea and an esophagus, andwherein the receive antenna is configured to receive the one or moreresultant signals containing information relating to the position andmotion of said muscles proximate to at least one of said trachea andsaid esophagus.
 15. A collar comprising: a housing containing aprocessor configured to control generation of an ultra-wideband radarsignal and reception of one or more resultant signals, said housinglocated at a first circumferential position on said collar; a transmitantenna, the transmit antenna configured to output the ultra-widebandradar signal directed at biological tissue, the transmit antenna havinga beam width; and a receive antenna, the receive antenna configured toreceive the one or more resultant signals resulting from a reflection ofthe ultra-wideband radar signal from the biological tissue, the receiveantenna having a beam width; wherein the transmit antenna and thereceive antenna are located in the housing, and wherein the transmitantenna is located at a fixed angle relative to the receive antenna tomaximize a magnitude associated with the one or more resultant signalssuch that the beam width of the transmit antenna is configured tooverlap with the beam width of the receive antenna at the biologicaltissue.
 16. The collar according to claim 15, wherein the transmitantenna is a first transmit antenna, wherein the receive antenna is afirst receive antenna, and wherein the collar further comprises: asecond transmit antenna; and a second receive antenna, and wherein thesecond transmit antenna and the second receive antenna are located at asecond circumferential position separate from the first circumferentialposition.
 17. The collar according to claim 15, wherein the transmitantenna is configured to output the ultra-wideband signal to illuminateat least one of a carotid artery and a jugular vein, and wherein thereceive antenna is configured to receive the one or more resultantsignals containing information relating to the position and motion ofsaid at least one of the carotid artery and the jugular vein.
 18. Thecollar according to claim 15, wherein the transmit antenna is configuredto output the ultra-wideband signal to illuminate muscles proximate toat least one of a trachea and an esophagus, and wherein the receiveantenna is configured to receive the one or more resultant signalscontaining information relating to the position and motion of saidmuscles proximate to at least one of said trachea and said esophagus.19. The collar according to claim 1, wherein the angle is based on atype of tissue associated with the biological tissue.
 20. The collaraccording to claim 1, wherein the angle is based on one or morestructures between the biological tissue and at least one of thetransmit antenna or the receive antenna.
 21. The collar according toclaim 1, wherein the angle is based on a type of physiological signalassociated with the biological tissue.
 22. The collar according to claim15, wherein the angle is based on a type of tissue associated with thebiological tissue.
 23. The collar according to claim 15, wherein theangle is based on one or more structures between the biological tissueand at least one of the transmit antenna or the receive antenna.
 24. Thecollar according to claim 15, wherein the angle is based on a type ofphysiological signal associated with the biological tissue.